The invention relates to a cruise control system and method for vehicles of all types (for example, motor vehicles, railway vehicles, trucks, military vehicles, caterpillar-type vehicles, two wheeled vehicles, vehicles with internal combustion engines, hybrid drive systems, electric drive systems or solar drive systems etc.) for consumption-oriented control of the speed of the vehicle within a predefined desired speed range.
Vehicles with cruise control systems have existed for a long time. Most of the cruise control systems that are commercially available at the present time control the speed of the vehicle by way of a predefined desired speed. These systems are suitable predominantly for trips on roads with low traffic congestion, because in this case driving at a constant speed is often desired.
Today it is possible to obtain from some manufacturers not only these cruise control systems, but also cruise control systems that are expanded to include an inter-vehicle distance control system. In principle, the well-known cruise control system, which maintains a certain predefined desired speed, is expanded to include an additional inter-vehicle distance control function, so that the use of such an “inter-vehicle distance-dependent” cruise control system becomes possible even in congested freeway and country road traffic. This so-called “inter-vehicle distance-dependent cruise control system” maintains the predefined desired speed, when one's own lane is clear. If an inter-vehicle distance sensor system, which is mounted on the motor vehicle and which can work, in particular, based on radar, detects a target object, in particular a (motor) vehicle traveling ahead in the same lane, then one's own speed is adjusted to the speed of the motor vehicle traveling ahead by, for example, effecting a suitable braking torque. To some extent such systems can control the speed as far as up to the stationary state when the vehicle is following another vehicle.
In addition to these conventional cruise control systems, there also exist cruise control systems wherein the speed of the vehicle is not varied with respect to a predefined desired speed, but rather is varied within a predefined speed range in such a way that the result is optimal consumption. For example, DE 102 05 226 A1 discloses a device for adjusting the speed to a set desired value by automatically regulating or controlling the drive unit. In this case the desired value is assigned a range of values, in which the desired value lies. However, the system does not intervene until the speed of the vehicle is outside the range of values. If, for example, the vehicle is driving uphill, then this feature results in a rapid decrease in the speed within the range of values. That is, there is no correction. Not until the lower limit of the value range has been reached is there an acceleration. With such a design of the cruise control system it is possible to save fuel. However, since this system does not intervene until one of the two limits of the value range has been reached, on reaching the lower limit for the first time, the vehicle is maintained continuously at this speed.
DE 10 2005 017 965 A1 discloses a combination of a cruise control system for controlling the speed with respect to a predefined desired value and a fuel regulating system for regulating the fuel consumption with respect to a predefined fuel consumption value or up to a maximum fuel consumption value. In this case the fuel consumption regulation is given higher priority. If, for example, it is not possible to maintain or reach the predefined desired speed while simultaneously taking into consideration the predefined (maximum) fuel consumption value, then the cruise control system is deactivated, or another desired speed is preset. The drawback with such a system is that very soon the situation may arise that the desired speed can no longer be maintained. Then the cruise control system would be deactivated. In this situation an automatic cruise control is hardly possible or is possible for just a very short period of time. Since the fuel consumption value may not be exceeded, at each ascent the vehicle would move forward at just a very slow rate. Under some circumstances the vehicle would even stop, because the fuel consumption value cannot be maintained. This process can lead to dangerous traffic situations.
An object of the invention is to provide an improved cruise control system for consumption-oriented speed control. On the one hand, optimal fuel reduction and, on the other hand, comfortable and convenient driving become possible with this cruise control system without simultaneously constituting a traffic obstruction. Furthermore, it shall be possible to integrate this cruise control system into, for example, an inter-vehicle distance monitoring “Tempomat” (ACC [adaptive cruise control]) or into a Tempomat with brake engagement (DCC [dynamic cruise control]).
This and other objects are achieved with a cruise control system and method for vehicles in accordance with the invention. In this case the vehicle speed for consumption-oriented control is not controlled with respect to a desired speed, but rather within a predefined desired speed range. The cruise control system includes at least one operating unit for activating the consumption-oriented speed control and a control unit, which controls the vehicle speed within the predefined desired speed range by controlling the drive unit when the consumption-oriented speed control is activated. The vehicle speed is controlled as a function of the consumption-oriented speed control while simultaneously taking into consideration a predefined maximum energy consumption value such that the predefined maximum energy consumption value is not exceeded only as long as a vehicle speed that lies within the predefined desired speed range is adjustable while taking into consideration the energy consumption value. That is, within the desired speed range the energy supply for the drive unit is reduced to a maximum energy consumption value. If it is no longer possible to adjust the speed to a speed within the predefined desired speed range, then there is no need to consider the predefined energy consumption value for the purpose of speed control. That is, the speed control is given higher priority than the consideration of the predefined maximum energy consumption value.
The maximum energy consumption value (or rather the reduced energy supply) is preset, for example, as a function of a known or determined, engine-specific average consumption value—in particular, as a function of the engine-specific average consumption, as defined by the EC directive 93/116/EEC European driving cycle. Depending on the drive unit that is installed into the vehicle (for example, an internal combustion engine, electric engine, hybrid drive, solar drive, etc.), the energy consumption value involves, for example, a fuel consumption value and/or an energy consumption value, which reflects the consumption of the corresponding energy for the drive.
In a first alternative the desired speed range can be preset by the system in such a way that the result is a comfortable speed for a specific mode of driving (for example, city driving mode, country road mode or freeway mode) for the driver. For example, for the country road mode in Germany a desired speed range between 85 km/h and 100 km/h would be conceivable, and for driving on the freeway a desired speed range between 115 km/h and 135 km/h would be conceivable. A (significantly) higher upper limit of the desired speed range in the freeway driving mode is not necessarily practical, because, on the one hand, the desired speed range should not be preset too wide, and, on the other hand, the driver does not usually pay any attention to the consumption when he wants a higher speed. Regardless, it is also possible to arrange for a high speed mode. However, in practice any desired speed range is feasible.
The limits of at least one desired speed range can be configured, for example, as a function of the predefined road or region-specific speed limits that in turn can be country-specific.
Ideally the limits of the desired speed range that are set by the system can be influenced by the driver within certain limits, so that the desired range can be adjusted even better to the driver's driving style in certain driving modes. Working on this basis, it is advisable to consider the respective country-specific, legally prescribed maximum speeds and/or also minimum speeds.
This first alternative provides in an advantageous way that the consumption-oriented speed control can be activated when a corresponding operating element is actuated (for example, by holding down the Tempomat lever for a long period of time) only if at the point-in-time, at which the operating element is actuated, the current vehicle speed lies within the predefined desired speed. Otherwise, for example, the conventional Tempomat intervenes.
If, for example, a number of desired speed ranges for different driving modes are preset by the system and these ranges do not advantageously overlap, then when the corresponding operating element for the consumption-oriented speed control is actuated, the system uses the desired speed range, within which the current speed lies. If the current speed lies in none of the predefined desired speed ranges, then the consumption-oriented speed control cannot be activated. Instead, it is possible to activate in an advantageous way a conventional speed control with respect to the current speed as the desired speed or another predefined desired speed.
In a second alternative it is assumed that the vehicle is equipped, for example, with an “ECO” button, which the driver has to activate before using the consumption-oriented speed control. By activating the “ECO” button, the vehicle is practically put into the state of driving in a consumption-oriented mode. If the “ECO” button is not activated, then only the conventional Tempomat functions. The vehicle state of driving in a consumption-oriented mode can be maintained until the driver deactivates again the corresponding operating element (for example, the “ECO” button). In the following description of this second alternative it is assumed that the “ECO” button is activated and that the vehicle is in a state, in which it is driving in the consumption-oriented mode.
In this second alternative, the desired speed range (or rather the limits of the desired speed range) can be preset as a function of the current vehicle speed when the request to activate the consumption-oriented speed control is recognized (actuation of the operating element for activating). That is, the driver can activate the consumption-oriented speed control at almost any current speed, as a result of which the desired speed range is then set based on the current speed of the vehicle.
Ideally, when the operating element for activating the consumption-oriented speed control is actuated, the current vehicle speed is set as the upper limit of the desired speed range. Then a lower speed that depends on the current speed, more particularly the upper limit, is set as the lower limit of the desired speed range. The lower speed can be set, for example, in such a way that the lower limit is less than the upper limit of the desired speed range by a predefined percentage (for example, 20%) or by a predefined (speed-dependent) absolute speed value. If, for example, the operating element for activating the consumption-oriented speed control is actuated at a current vehicle speed of 100 km/h, then the upper limit of the desired speed range is set at 100 km/h, and the lower limit is set at 80 km/h (upper threshold speed minus 20%). Similarly on activation at 150 km/h the upper limit of the desired speed range is set at 150 km/h, and the lower limit is set at 120 km/h. On activation at 50 km/h the desired speed range extends from 40 km/h to 50 km/h.
The advantage of this alternative for presetting the desired speed range is that the driver can activate the consumption-oriented speed control at any speed, and the presetting of the desired speed range is intuitive to the driver. In this way the driver defines the maximum speed, at which he wants to drive from first-hand experience.
As in conventional systems, the consumption-oriented speed control can be overridden temporarily by actuating the gas pedal at any time in order to accelerate. As soon the acceleration action has been completed, the consumption-oriented speed control does not respond again until the speed of the vehicle lies in the desired speed range. The vehicle is not abruptly decelerated, but rather continues to travel until the vehicle speed lies once again in the desired speed range. In any case the consumption-oriented speed control is deactivated immediately by actuating the brake pedal.
In one configuration the speed of the vehicle is adjusted within the predefined desired speed range during the consumption-oriented speed control in such a way that the result is the maximum possible speed while simultaneously taking into consideration the maximum energy consumption value.
As an alternative to the above, an additional configuration provides that the speed of the vehicle is adjusted within the predefined desired speed range during the consumption-oriented speed control in such a way that the result is the minimum possible speed while simultaneously taking into consideration the maximum energy consumption value.
Owing to the consideration of the maximum energy consumption value during the consumption-oriented speed control, the situation may arise that the vehicle speed can no longer be maintained within the desired speed range. In order to be able to reach again or maintain the desired speed range, the cruise control system is configured in such an advantageous manner that on reaching or undershooting the lower limit of the predefined desired speed range, the control unit no longer adjusts the speed of the vehicle in consideration of the predefined maximum energy consumption value, but rather independently thereof, so that the lower limit of the desired speed range can be reached again or maintained. This approach prevents the vehicle from becoming the cause of obstructing traffic. Such operating modes typically occur when traveling uphill. Especially in this case it is possible to set, independently of the energy consumption value, a vehicle speed that corresponds to at least the lower limit of the desired speed range, or is greater than said lower limit.
If the lower limit of the desired speed range can be adjusted again or at least maintained presumably even while taking into consideration the predefined maximum energy consumption value, then the speed control is executed again while taking into consideration the predefined maximum energy consumption value. Working on this basis, it is advantageous if the speed control, which is independent of the energy consumption value, is active only until a predefined first minimum speed within the desired speed range is reached, or until the predefined first minimum speed is reached and is maintained for a predefined first time interval by applying an energy consumption value that is at least no greater than the predefined maximum energy consumption value. The predefined first minimum speed value can be, for example, the lower limit of the desired speed range or greater than this lower limit.
In order to be able to save even more energy, it is possible in the case of vehicles with an automatically operable clutch to interrupt, on detecting a hill descent, the force closure between the drive unit and the transmission unit and/or the drivable wheels by opening the clutch, and the energy supply for the drive unit can be reduced so as to go to zero. According to a first alternative, this interruption of the force closure and the reduction in the energy supply can be executed, if a boost mode is present (that is, the energy consumption value goes to zero) and the vehicle speed within the desired speed range remains constant or rises. If this state is recognized by the control unit or is indicated by means of a respective signal, then the control unit sends out a force closure interrupt signal for interrupting the force closure between the drive unit and the transmission unit and/or the drivable wheels of the vehicle.
As an alternative, the control unit does not send out a force closure interrupt signal for interrupting the force closure between the drive unit and the transmission unit and/or the drivable wheels of the vehicle until the upper limit of the desired speed range is reached or exceeded. The strategy ensures that only after a suitable supply of energy does the vehicle reach as fast as possible the upper limit of the desired speed range, and only after the speed continues to increase nevertheless, (for example, owing to the boost mode) does the clutch open. A minimal overshooting of the upper limit of the desired speed range can occur, for example, due to the boost mode, because no automatic brake engagement takes place within the desired speed range during the consumption-oriented speed control.
In order to be able to hold or reach the predefined desired speed range, the brake engagement (in both alternatives) is initiated, so that the result is the maximum allowable vehicle speed that corresponds to the upper limit of the desired speed range.
If, in the event that the clutch is opened, a predefined second minimum speed is reached within the desired speed range without brake engagement or is maintained without brake engagement (that is, the downhill force is no longer present and the vehicle speed decreases), then the control unit sends out a force closure closing signal to restore the force closure between the drive unit and the transmission unit and/or the drivable wheels. Then the force closure is restored, and the speed control is performed again while simultaneously taking into consideration the predefined maximum energy consumption value in such a way that this maximum energy consumption value is not exceeded. The upper limit of the desired speed range or the lower limit of the desired speed range or any speed within the desired speed range can be preset as the second minimum speed.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.